From: Junio C Hamano <gitster@pobox.com>
To: "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, me@ttaylorr.com, l.s.r@web.de,
szeder.dev@gmail.com, Chris Torek <chris.torek@gmail.com>,
Derrick Stolee <stolee@gmail.com>,
Derrick Stolee <derrickstolee@github.com>,
Derrick Stolee <dstolee@microsoft.com>,
Han-Wen Nienhuys <hanwen@google.com>
Subject: Re: [PATCH v4 17/17] chunk-format: add technical docs
Date: Thu, 18 Feb 2021 13:47:51 -0800 [thread overview]
Message-ID: <xmqqft1tdp4o.fsf@gitster.g> (raw)
In-Reply-To: <84bf6506dc12163b37f46192b3742c8fb234322f.1613657260.git.gitgitgadget@gmail.com> (Derrick Stolee via GitGitGadget's message of "Thu, 18 Feb 2021 14:07:39 +0000")
"Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:
> +Chunk-based file formats
> +========================
> +
> +Some file formats in Git use a common concept of "chunks" to describe
> +sections of the file. This allows structured access to a large file by
> +scanning a small "table of contents" for the remaining data. This common
> +format is used by the `commit-graph` and `multi-pack-index` files. See
> +link:technical/pack-format.html[the `multi-pack-index` format] and
> +link:technical/commit-graph-format.html[the `commit-graph` format] for
> +how they use the chunks to describe structured data.
I've read the doc added here to the end; well written and easy to
understand.
I wonder how/if well reftable files fit in the scheme, or if it
doesn't, should the chunk file format API be updated to accomodate
it (or the other way around)?
> +Extract the data information for each chunk using `pair_chunk()` or
> +`read_chunk()`:
> +
> +* `pair_chunk()` assigns a given pointer with the location inside the
> + memory-mapped file corresponding to that chunk's offset. If the chunk
> + does not exist, then the pointer is not modified.
I think it is worth adding:
The caller is expected to know where the returned chunk ends by
some out-of-band means, as this function only gives the offset
but not the size, unlike the read_chunk() function.
> +* `read_chunk()` takes a `chunk_read_fn` function pointer and calls it
> + with the appropriate initial pointer and size information. The function
> + is not called if the chunk does not exist. Use this method to read chunks
> + if you need to perform immediate parsing or if you need to execute logic
> + based on the size of the chunk.
> +
> +After calling these methods, call `free_chunkfile()` to clear the
> +`struct chunkfile` data. This will not close the memory-mapped region.
> +Callers are expected to own that data for the timeframe the pointers into
> +the region are needed.
Thanks.
next prev parent reply other threads:[~2021-02-18 21:48 UTC|newest]
Thread overview: 120+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-26 16:01 [PATCH 00/17] Refactor chunk-format into an API Derrick Stolee via GitGitGadget
2021-01-26 16:01 ` [PATCH 01/17] commit-graph: anonymize data in chunk_write_fn Derrick Stolee via GitGitGadget
2021-01-27 1:53 ` Chris Torek
2021-01-27 2:36 ` Taylor Blau
2021-01-26 16:01 ` [PATCH 02/17] chunk-format: create chunk format write API Derrick Stolee via GitGitGadget
2021-01-27 2:42 ` Taylor Blau
2021-01-27 13:49 ` Derrick Stolee
2021-01-26 16:01 ` [PATCH 03/17] commit-graph: use chunk-format " Derrick Stolee via GitGitGadget
2021-01-27 2:47 ` Taylor Blau
2021-01-26 16:01 ` [PATCH 04/17] midx: rename pack_info to write_midx_context Derrick Stolee via GitGitGadget
2021-01-27 2:49 ` Taylor Blau
2021-01-26 16:01 ` [PATCH 05/17] midx: use context in write_midx_pack_names() Derrick Stolee via GitGitGadget
2021-01-26 16:01 ` [PATCH 06/17] midx: add entries to write_midx_context Derrick Stolee via GitGitGadget
2021-01-26 16:01 ` [PATCH 07/17] midx: add pack_perm " Derrick Stolee via GitGitGadget
2021-01-26 16:01 ` [PATCH 08/17] midx: add num_large_offsets " Derrick Stolee via GitGitGadget
2021-01-26 16:01 ` [PATCH 09/17] midx: return success/failure in chunk write methods Derrick Stolee via GitGitGadget
2021-01-26 16:01 ` [PATCH 10/17] midx: drop chunk progress during write Derrick Stolee via GitGitGadget
2021-01-26 16:01 ` [PATCH 11/17] midx: use chunk-format API in write_midx_internal() Derrick Stolee via GitGitGadget
2021-01-26 16:01 ` [PATCH 12/17] chunk-format: create read chunk API Derrick Stolee via GitGitGadget
2021-01-27 3:02 ` Taylor Blau
2021-01-26 16:01 ` [PATCH 13/17] commit-graph: use chunk-format read API Derrick Stolee via GitGitGadget
2021-01-26 16:01 ` [PATCH 14/17] midx: " Derrick Stolee via GitGitGadget
2021-01-27 3:06 ` Taylor Blau
2021-01-27 13:50 ` Derrick Stolee
2021-01-26 16:01 ` [PATCH 15/17] midx: use 64-bit multiplication for chunk sizes Derrick Stolee via GitGitGadget
2021-01-26 16:01 ` [PATCH 16/17] chunk-format: restore duplicate chunk checks Derrick Stolee via GitGitGadget
2021-01-26 16:01 ` [PATCH 17/17] chunk-format: add technical docs Derrick Stolee via GitGitGadget
2021-01-26 22:37 ` [PATCH 00/17] Refactor chunk-format into an API Junio C Hamano
2021-01-27 2:29 ` Taylor Blau
2021-01-27 15:01 ` [PATCH v2 " Derrick Stolee via GitGitGadget
2021-01-27 15:01 ` [PATCH v2 01/17] commit-graph: anonymize data in chunk_write_fn Derrick Stolee via GitGitGadget
2021-01-27 15:01 ` [PATCH v2 02/17] chunk-format: create chunk format write API Derrick Stolee via GitGitGadget
2021-02-04 21:24 ` Junio C Hamano
2021-02-04 22:40 ` Junio C Hamano
2021-02-05 11:37 ` Derrick Stolee
2021-02-05 19:25 ` Junio C Hamano
2021-01-27 15:01 ` [PATCH v2 03/17] commit-graph: use chunk-format " Derrick Stolee via GitGitGadget
2021-01-27 15:01 ` [PATCH v2 04/17] midx: rename pack_info to write_midx_context Derrick Stolee via GitGitGadget
2021-01-27 15:01 ` [PATCH v2 05/17] midx: use context in write_midx_pack_names() Derrick Stolee via GitGitGadget
2021-01-27 15:01 ` [PATCH v2 06/17] midx: add entries to write_midx_context Derrick Stolee via GitGitGadget
2021-01-27 15:01 ` [PATCH v2 07/17] midx: add pack_perm " Derrick Stolee via GitGitGadget
2021-01-27 15:01 ` [PATCH v2 08/17] midx: add num_large_offsets " Derrick Stolee via GitGitGadget
2021-01-27 15:01 ` [PATCH v2 09/17] midx: return success/failure in chunk write methods Derrick Stolee via GitGitGadget
2021-02-04 22:59 ` Junio C Hamano
2021-02-05 11:42 ` Derrick Stolee
2021-01-27 15:01 ` [PATCH v2 10/17] midx: drop chunk progress during write Derrick Stolee via GitGitGadget
2021-01-27 15:01 ` [PATCH v2 11/17] midx: use chunk-format API in write_midx_internal() Derrick Stolee via GitGitGadget
2021-01-27 15:01 ` [PATCH v2 12/17] chunk-format: create read chunk API Derrick Stolee via GitGitGadget
2021-02-04 23:40 ` Junio C Hamano
2021-02-05 12:19 ` Derrick Stolee
2021-02-05 19:37 ` Junio C Hamano
2021-02-08 22:26 ` Junio C Hamano
2021-02-09 1:33 ` Derrick Stolee
2021-02-09 20:47 ` Junio C Hamano
2021-01-27 15:01 ` [PATCH v2 13/17] commit-graph: use chunk-format read API Derrick Stolee via GitGitGadget
2021-01-27 15:01 ` [PATCH v2 14/17] midx: " Derrick Stolee via GitGitGadget
2021-01-27 15:01 ` [PATCH v2 15/17] midx: use 64-bit multiplication for chunk sizes Derrick Stolee via GitGitGadget
2021-02-05 0:00 ` Junio C Hamano
2021-02-05 10:59 ` Chris Torek
2021-02-05 20:41 ` Junio C Hamano
2021-02-06 20:35 ` Chris Torek
2021-02-05 12:30 ` Derrick Stolee
2021-02-05 19:42 ` Junio C Hamano
2021-02-07 19:50 ` SZEDER Gábor
2021-02-08 5:41 ` Junio C Hamano
2021-01-27 15:01 ` [PATCH v2 16/17] chunk-format: restore duplicate chunk checks Derrick Stolee via GitGitGadget
2021-02-05 0:05 ` Junio C Hamano
2021-02-05 12:31 ` Derrick Stolee
2021-01-27 15:01 ` [PATCH v2 17/17] chunk-format: add technical docs Derrick Stolee via GitGitGadget
2021-02-05 0:15 ` Junio C Hamano
2021-01-27 16:03 ` [PATCH v2 00/17] Refactor chunk-format into an API Taylor Blau
2021-02-05 2:08 ` Junio C Hamano
2021-02-05 2:27 ` Derrick Stolee
2021-02-05 14:30 ` [PATCH v3 " Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 01/17] commit-graph: anonymize data in chunk_write_fn Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 02/17] chunk-format: create chunk format write API Derrick Stolee via GitGitGadget
2021-02-07 21:13 ` SZEDER Gábor
2021-02-08 13:44 ` Derrick Stolee
2021-02-11 19:43 ` SZEDER Gábor
2021-02-05 14:30 ` [PATCH v3 03/17] commit-graph: use chunk-format " Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 04/17] midx: rename pack_info to write_midx_context Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 05/17] midx: use context in write_midx_pack_names() Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 06/17] midx: add entries to write_midx_context Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 07/17] midx: add pack_perm " Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 08/17] midx: add num_large_offsets " Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 09/17] midx: return success/failure in chunk write methods Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 10/17] midx: drop chunk progress during write Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 11/17] midx: use chunk-format API in write_midx_internal() Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 12/17] chunk-format: create read chunk API Derrick Stolee via GitGitGadget
2021-02-07 20:20 ` SZEDER Gábor
2021-02-08 13:35 ` Derrick Stolee
2021-02-05 14:30 ` [PATCH v3 13/17] commit-graph: use chunk-format read API Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 14/17] midx: " Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 15/17] midx: use 64-bit multiplication for chunk sizes Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 16/17] chunk-format: restore duplicate chunk checks Derrick Stolee via GitGitGadget
2021-02-05 14:30 ` [PATCH v3 17/17] chunk-format: add technical docs Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 00/17] Refactor chunk-format into an API Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 01/17] commit-graph: anonymize data in chunk_write_fn Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 02/17] chunk-format: create chunk format write API Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 03/17] commit-graph: use chunk-format " Derrick Stolee via GitGitGadget
2021-02-24 16:52 ` SZEDER Gábor
2021-02-24 17:12 ` Taylor Blau
2021-02-24 17:52 ` Derrick Stolee
2021-02-24 19:44 ` Junio C Hamano
2021-02-18 14:07 ` [PATCH v4 04/17] midx: rename pack_info to write_midx_context Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 05/17] midx: use context in write_midx_pack_names() Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 06/17] midx: add entries to write_midx_context Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 07/17] midx: add pack_perm " Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 08/17] midx: add num_large_offsets " Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 09/17] midx: return success/failure in chunk write methods Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 10/17] midx: drop chunk progress during write Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 11/17] midx: use chunk-format API in write_midx_internal() Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 12/17] chunk-format: create read chunk API Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 13/17] commit-graph: use chunk-format read API Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 14/17] midx: " Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 15/17] midx: use 64-bit multiplication for chunk sizes Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 16/17] chunk-format: restore duplicate chunk checks Derrick Stolee via GitGitGadget
2021-02-18 14:07 ` [PATCH v4 17/17] chunk-format: add technical docs Derrick Stolee via GitGitGadget
2021-02-18 21:47 ` Junio C Hamano [this message]
2021-02-19 12:42 ` Derrick Stolee
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